1. Field of the Invention
The present invention relates to a vane pump apparatus and a leak check system having the same.
2. Description of Related Art
For instance, Japanese Unexamined Patent Publication No. 2007-218161A (corresponding to US20070189907A1) teaches a leak check system that executes leak check of an evaporative emission system, which is adapted to purge fuel vapor generated in a fuel tank into an intake passage of an internal combustion engine, based on a pressure that is sensed at the time of depressurizing or pressurizing the evaporative emission system by a pump. In this leak check system, a vane pump is used as the pump, which depressurizes or pressurizes a gas. In the vane pump, a rotor is eccentrically received in a housing, and vanes are slidably received in the rotor in a manner that enables radial reciprocation of the vanes relative to the rotor. In this type of vane rotor, when moisture is condensed to water at the rotor and the vanes, the condensed water may possibly cause the vanes to stick to the rotor. In this state, even when the rotor is rotated by an electric motor, the vanes cannot be airtightly slid along an inner peripheral wall of the housing, so that the gas cannot be sufficiently depressurized or pressurized by the vane pump.
In the leak check system of Japanese Unexamined Patent Publication No. 2007-218161A (corresponding to US20070189907A1), prior to the execution of the leak check, the vane pump is driven to depressurize or pressurizes the gas, and a pressure of the depressurized or pressurized gas is sensed. At this time, in a case where the sensed pressure deviates from a normal range on the atmospheric pressure side, and a value of an electric current of the motor is larger than a normal range, it is determined that an abnormality of sticking of the vanes to the rotor occurs due to, for example, the presence of the condensed water. Then, the motor is driven in a manner that eliminates the condensed water, which causes the sticking of the vanes to the rotor.
When abrasion powder, which is generated from the rotor, the vanes and the housing, is accumulated in the housing, a degree of sealing of the housing may possibly be improved. In such a state where the degree of sealing of the housing is improved by the abrasion powder, the sensed pressure may possibly fall in the normal range even in the presence of the condensed water at the rotor and the vanes. In the leak check system of Japanese Unexamined Patent Publication No. 2007-218161A (corresponding to US20070189907A1), the pressure measured at the time of depressurization or pressurization is compared with the normal range thereof before the comparison of the current value of the motor with the normal range thereof. Therefore, the presence of the condensed water, which results in the falling of the sensed pressure within the normal range, cannot be sensed. Thus, when the condensed water is eliminated during the leak check while the abrasion power is kept held in the housing, an erroneous determination of the normality (absence of the leak) may possibly occur even though the leak actually exists.
Japanese Patent No. 421496582 (corresponding to US2006/0016253A1) teaches leak check, which is executed while the electric motor is rotated at a stored rotational speed, which has been stored in a memory and at which a pressure sensed at the time of depressurizing or pressurizing with the vane pump becomes a reference pressure. In this leak check system, in the case where the degree of sealing is improved by the accumulation of the abrasion powder during the leak check, when the motor is rotated at the stored rotational speed, an erroneous determination of the normality (absence of the leak) may possibly occur even though the leak actually exists like in the case of the leak check system of Japanese Unexamined Patent Publication No. 2007-218161A (corresponding to US20070189907A1).